The India Meteorological Department (IMD) has found that in 2018 citizens across a vast swathe of India suffered from heat wave for over 50 days spanning April, May and June. The heatwave days were 25 in May and 17 in June. Interestingly, April also reported 12 days of heatwave last year. The IMD had forecast last year that in 2019, along with expected increase in the duration and frequency of heat waves, numbers of hot days are also expected to increase.
As per the IMD, heatwave is considered if maximum temperature of a station reaches at least 40°C or more for plains, 37°C or more for coastal stations and at least 30°C or more for Hilly regions.
The regions falling under the core heat wave zone are Delhi, Punjab, Haryana, Rajasthan, Himachal Pradesh, Uttarakhand, Uttar Pradesh, Gujarat, Madhya Pradesh, Chhattisgarh, Bihar, Jharkhand, West Bengal, Orissa and Telangana, and meteorological subdivisions of Marathwada, Vidarbha, central Maharashtra and coastal Andhra Pradesh.
"The heat wave was reported over some parts of Rajasthan, Madhya Pradesh, Vidarbha, northeast, Jammu & Kashmir, Odisha, cCoastal Andhra Pradesh and along west coast. Over some parts of Kerala, maximum temperature was greater than 90th percentile for more than 50 to 60 % of the days in April, May and June," the IMD report said.
According to report, there were many underlying mechanisms which contribute to the development of a heat wave. "It can form when a warm high pressure system stalls in a region. The high and the associated anti cyclonic flow cause a sinking motion which leads to increased surface temperatures due to adiabatic compression. The outward anti cyclonic flow makes it difficult for other systems to enter the area. Variations in jet stream, flow of air that steers movement of high and low pressure areas which transports hot dry air into a region were favorable conditions for development of heat wave," it said.
In 2018, there were 70 tropical cyclones all over the world, while the long term average is 53. Due to impacts of warmer surface temperatures and more ocean heat will be greater occurrence of extreme weather events such as tropical cyclones, heat waves, floods and droughts.
The IMD has predicted the average temperature in most parts of north India northeast regions, northwest India and southern parts of west coast to remain higher than normal by 0.5-1.0 degree Celsius during March, April, May this year. The rest part of the country is expected to see normal temperature during summer. "The heat wave is expected to hit 16 States due to various reasons in 2019. However, normal heat wave - like conditions will prevail over the country's core heat wave zone. Central and northern India are generally considered the core heat wave zones," IMD officials said.
The past four years, from 2015 to 2018, were the warmest ever recorded years. In fact, the 20 warmest years on record have occurred in the last 22 years. This trend also sits in perfectly with the emission rates of greenhouse gases (GHGs), which were at a record high in 2018 according to the World Meteorological Organisation (WMO).
As per latest Global climate risk index 2019 report, the world lost more than 5 lakh people to such events in the last 20 years along with an economic loss of $ 3.47 trillion.